Distributed computing environment

ABSTRACT

A very large number of applications communicate logically through a many-to-many multicast cloud on the common carrier Internet. Three types of systems operate together to implement the method. The first is a network enabled client application, such as a distributed simulation or game, which joins an application cloud or federation and communicates its internal state changes into the cloud via a communication applications programming interface. The second is a lobby manager or broker which accepts entry into a communication cloud or federation and provides information to the federation and the client application for establishing communications between them. And third, is an application-specific routing system which provides the normal function of routing packets between Internet hosts (client applications running on these hosts), but also allows the routing functions to affected by modules in the router which are associated with the distributed application or simulation being implemented.

REFERENCE TO PRIOR APPLICATION

This application is a continuation of U.S. patent application Ser. No.09/785,385, filed Feb. 16, 2001, which claims priority of U.S.provisional application Ser. No. 60/192,977, filed Mar. 28, 2000, theentire content of both of which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to network computing and, moreparticularly, to a distributed environment that supports massivegroupware streaming and pier-to-pier packetized communications.

BACKGROUND OF THE INVENTION

Computer games and simulations, like most computer applications, havetraditionally been limited to single play units (i.e. a single consolewhich creates the display and is operated through one or several controldevices or pads). The PC, because it can be networked via modems, onlocal network, or the internet, has opened up the possibility of gamesin which multiple player interact with each other.

Earlier work in this area describes one player connected to a singleother player with simple modems. U.S. Pat. Nos. 5,292,125 and 5,350,176to Hochstein and U.S. Pat. No. 5,538,255 to Barker describe computergame systems which can allow synchronized play between two playersconnect by a modem.

Later work, like U.S. Pat. Nos. 5,558,339, 5,896,444, and 5,956,485 toPerlman, describe small scale “client-server” models where a client cameconnects to a game server through a network. Because of game play modelsof this type being limited in the number of players which must besupported, most current PC games of this type allow a small number ofplayers to interact, perhaps 10-30 players on a local area computernetwork. For small scale client-server games, the server can be simpleand need not be optimized for the number of communication connectionsnor for quick/efficient access to game/client specific parameters.

Several newly release games, like Ultima Online and Everquest haveexpanded network player counts to the 1000-10,000 level. To achieve thislevel of multiple player interaction, these games use specializedcentral servers (or server clusters which are closely linked) which runprograms that understand about all the players and how they interactwith each other, thus, the individual player game systems are notcomplete without the central servers or server clusters. This technologyhas been described in the patent literature by U.S. Pat. No. 5,659,691to Durward; U.S. Pat. No. 5,664,778 to Kikuchi and U.S. Pat. No.5,668,950. U.S. Pat. No. 5,828,866 Hao et al. use the same concepts todistribute data in distributed CAD applications.

For the last several years, an alternative model for massive distributedplay has been developed by elements of the U.S. Department of Defenseand its contractors. This model is call “distributed simulation” becausein its pure implementation, each client broadcasts its internal statechanges (for instance object motions) to the network and reads all statechanges from other clients to depict simulation changes which arecomputed on other client systems. Thus, no central server is needed tomake the distributed system operate. The significant advantage of thedistributed approach is that there is not a bottleneck at a centralserver (or server cluster), because each client can send data to anotherwithout going directly through a server.

The basics of this method of connecting applications into a network wererefined from about 1985 to 1990 in a program generally name SIMNET.SIMNET technology was later renamed as DIS or Distributed InteractiveSimulation. Some same publications from that period include Kraemer etal. (1987), Alluisi (1991), the DIS Steering Committee (1994), Calvin etal. (1995), Cosby (1995), Pullen et al. (1995) and later formalspecifications documents from the IEEE (1278.1 and 1278.2 published in1993 and 1995). Current Defense Department standards pertaining todistributed simulation, called the High Level Architecture or HLA, arepublished by the Defense Modeling and Simulation Office (1996).

In reality, some centralized functions still remain like finding all theplayers currently operating in the same distributed simulation space (sothat the client can send and receive from them, the client needs to knowtheir Internet or IP address). U.S. Pat. No. 5,685,775 to Bakogludescribes implementation of system like SIMNET but for operation viastandard dial-up phone networking (SIMNET, DIS, and HLA have alwaysassumed Internet LAN/WAN network architectures for higher state exchangerates). U.S. Pat. No. 5,775,996 to Othmer and U.S. Pat. No. 5,956,485 toPerlman describe brokering mechanisms which were similar to thoseintegral to SINET systems as early as 1989. U.S. Pat. No. 5,899,810 toSmith and U.S. Pat. No. 6,006,254 to Waters et al. are examples ofcommercially targeted systems which were influenced by the DIS and HLAarchitecture.

Similarly, it may be advantageous to access certain centralizeddatabases and files (like common descriptions of play area virtualterrain). These centralized functions, however, are characterized asbeing needed when a new client joins the simulations and when it leavesit. Thus, the more limited server is usually called a simulation broker,and can actually be implemented as part of the first client whichinitiates new simulated space. Centralized database distributions aredescribed in U.S. Pat. No. 5,659,691 to Durward; U.S. Pat. No. 5,984,786to Ehrrman; and U.S. Pat. No. 6,006,254 to Waters et al., but none ofthese focus only on data needed only for joining, and rather, in thespirit of client-server multiplay, provide databases from centralizedpoints which interact intimately with on-going game playing.

For simulations like those performed in military training, overrelatively high-speed networks, this advantage can be realized. However,if the simulation client is operating through a lower performance linklike a dial-up modern, replicating packets to all other clients in alarge pool (potentially including 1000+ clients) is not practical (i.e.the speed of transmission over the slow link precludes sending to manyclients at once). This problem at the client communication end hasmotivate most of the client-server type solutions referenced (HochsteinU.S. Pat. No. 5,292,125 and U.S. Pat. No. 5,350,176, Barker U.S. Pat.No. 5,538,255—only two players at a time; Perlman U.S. Pat. Nos.5,558,339, 5,896,444, 5,956,485, Durward et al. U.S. Pat. No. 5,659,691,Kikuchi et al. U.S. Pat. Nos. 5,664,778, 5,668,950, Bakoglu et al. U.S.Pat. No. 5,685,775, Barrus U.S. Pat. No. 5,736,990—small numbers ofplayers over bandwidth limited networks; Smith U.S. Pat. No. 5,899,810,Ehrman U.S. Pat. No. 5,984,786, Water et al. U.S. Pat. No. 6,006,254,Vange et al. U.S. Pat. No. 6,050,098, Kappler U.S. Pat. No.6,064,677—combination of distributed, client-server, and messagepriority queuing to improve performance in the network and on thecentral server). Work to overcome aspects of the problems which arisebecause of poor server or network performance are described by Barruset. al. U.S. Pat. No. 5,736,990, Othmer et al. U.S. Pat. No. 5,775,996,O'Callaghan U.S. Pat. No. 5,820,463, Waters U.S. Pat. No. 5,920,862,Lambright et al. U.S. Pat. No. 6,015,348, Vange et al. U.S. Pat. No.6,050,098, and Kappler U.S. Pat. No. 6,064,677.

One solution to this problem is inserting a repeater router, which readspackets from each client and resends them to all relevant other clientswhich need to see the particular state change. In a simple form this hasalready been defined for the Internet using a concept called multicast.In multicast, a source client and all of its destination peers establisha multicast connection so that when the client sends its packet onceinto the Internet, properly featured Internet routers (which are reallyin this case servers with repeater routers) replicate that packet androute it to all destination clients without the source client sendingthe data out multiple times.

Some replication methods used in multicast have described by Chen et al.U.S. Pat. No. 5,666,360 and in numerous Internet published Request ForComment (RFC—these publicly distributed papers describe allinteroperability standards used to implement the modem Internet and itsprotocols for data exchange; RFC are solicited and published by theInternet Society). Some RFC and papers defining details of InternetProtocol (IP) based multicasting are defined in Deering, RFC 1112,Pullen et al. (1995), Armitage RFC 2022 and RFC 2191, Fenner RFC 1112,Talpade et al. RFC 2149, and Pullen et al. RFC 2502 and RFC 2490.

Multicast, as built into some Internet routers and backbones, isconceptually very simple. One packet from a source goes in and multiplepackets to multiple clients go out (more or less by copying orreplicating the input packet). The service as currently designed hasbeen built for replication data from one point in to many out to delivermedia like digital video or digital audio (the digital Internetequivalent to broadcast TV or radio). For this type of use, there is noway to reduce replication effort through knowledge of the data beingsent—if a client is “tuned” to a digital TV station, it needs copies ofthe packets being sent from that station (or packet source).

Some of the RFC disclosed applications specific streaming protocols foraudio, video, and other data are defined in Schulzrinne, “RTP Profilefor Audio and Video Conferences with Minimal Control,” RFC 1890;Schulzrinne et al., “RTP: A Transport Protocol for Real-TimeApplications,” RFC 1889 and Real Time Streaming Protocol (RTSP), “RFC2326; Defense Modeling and Simulation Office, High Level ArchitectureRiles Version 1.0; Handley et al., “SDP: Session Description Protocol,”RFC 2327, and Arango et al., “Media Gateway Control Protocol (MGCP)Version 1.0,” RFC 2706.

In Pullen et al., “A Simulation Model for IP Multicast with RSVP,” RFC2490, the authors point out a number of deficiencies in using current IPmulticast to service distributed simulation. These center around thedifficulty in allowing a specific simulation client into and out ofmulticast groups (i.e. groups which will need the clients statebroadcast packets) quickly (presumably due to some application cullingrule changes as a client simulation executes). This presumes that makingand breaking multicast group membership is the best way to optimizepacket flows.

However, rather than making multicast more efficient (which is certainlya good idea, especially for applications independent uses) indistributed simulation and gaming, an alternative of making the routingsystem more intelligent about what and where data is needed can alsohave a significant impact on overall group or federation performance.Consider that quite a bit of knowledge is available about the source anddestination clients and the objects being simulated or displayed onthese clients. For instance, if the object on a client station whichrepresent client avatar (or player self) in the game is in one place, itwill not be able to see another object being simulated by another clientif that object is (1) behind a wall, (2) too far away, (3) moving tooquickly, (4) obscured by smoke or weather, to name a few simple cullingrules.

Similarly, since each object is a depiction of something withacceleration and mass properties, it cannot change is location,velocity, or acceleration outside of some operating envelope. This meansthat each client can track objects and predict within some error boundwhere they will be at each point in the future. If the predicted valueis close enough to the value from the client where the object is beingcreated (and probably controlled by a player), its state changes neednot be sent to other clients which can used the predicted location.Updates are only required when predictions are different from actuallocation by a large enough amount to effect the quality of play.

Culling rules based on proximity in the network [Seaman U.S. Pat. No.5,644,571], proximity in virtual space [Barrus et al. U.S. Pat. No.5,736,990], [Waters et al. U.S. Pat. No. 5,841,980], [Waters U.S. Pat.No. 5,920,862], and [Lambright et al. U.S. Pat. No. 6,015,348], andpriority [Vange et al. U.S. Pat. No. 6,050,098] and [Kappler et al. U.S.Pat. No. 6,064,677] have been used in client-server systems. However,these concepts have not been extended into IP multicast or conventionalrouters.

The advantages of putting application-specific information actually intothe routing system are many. Backbone routers provide the highest levelof access to the Internet. Thus, routing data from lower echelonnetworks (and client-point-to-router connections) into an upper echelonrouter, which in turn, determines routing quality of service based onthe needs of the federation (i.e. the needs based on source anddestination state data which is available to the router because of therecord of past packet traffic through it), can substantially reduceoverall traffic over the backbone. Since network traffic is directlytranslatable to cost and performance, utilizing application (game)specific data routing performance and packet traffic reduction rulesreduces cost and while improving multiplay game play performance.Culling rules inserted into the router is a specific instance of theconcept of inserting portable applications or applets into the route.This is analogous to adding special purposed functionality to a generalpurpose web by adding applets (which might be downloaded into it).

SUMMARY OF THE INVENTION

This invention broadly resides in a network computing environment andmethod that facilitates many-to-many data streaming with substantialmessage culling as well as more standard network optimization such asconventional multicast and Internet host packet routing. The approachallows a very large (i.e., greater than 100,000) number of clientapplications to communicate logically through a multicast cloud over acommon carrier such as the Internet to implement massive groupwareconfigurations including distributed simulations, games, and clientselectable/controllable data services used to broadcast audio, video, orother digital data.

According to a preferred embodiment, the technology utilizes threeprimary components; namely: client software, lobby management, andspecialized routing functions. The client software, preferably throughan applications programming interface, or API, connects a game client toa lobby manager or broker to initiate entry or joining of a federation(or a game cloud made up of all active players). The lobby manager orbrokering software accepts initial client connection, provides a meansfor validating the client's simulation software (i.e. checks databasesand code bases for compatibility with the federation) and provides ameans for downloading data to correct deficiencies.

One or more routing systems accept attachments by clients upon directionof one or several lobby managers. The routing systems are able to applygame-specific packet culling rules to and from clients based onprogrammed logic supplied by qualified programming stations (centralrouter control stations, game lobby managers and/or clients depending onsecurity considerations). Thus, a router can exhibit applicationstream-specific behaviors in addition to normal packet routingbehaviors.

The technology in the preferred embodiment is designed to implementmassive distributed games and simulations, however, the technology isequally valuable in implementing other massive groupware Internetapplications which benefit from special purpose applets which can bedownloaded and executed within the router triggered as part of routermessage flow control. An example is the distribution of usercustomizable video, audio, or other digitized information (like medicaldata).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the structure of the RTI implemented per the DMSOspecification;

FIG. 2 shows the invention's use of a separated routing function and alobby manager function;

FIG. 3 is a diagram that illustrates how processes for the samefederation on various router machines are able to communicate and routeclient messages from one to another;

FIG. 4 shows a sample network connecting seven clients to one of tworepeater routers through a single LobbyManager;

FIG. 5 is a diagram that shows how a status update need not need to bedone 10 times for each client connected to repeater router 2 between therepeater routers;

FIG. 6 shows how, if one starts with “CybernetBaseEntity”, whichconsists of double Altitude, double Latitude, and double Longitude, onecan define a culling “member function called “CheckCube” for“CybernetBaseEntity”;

FIG. 7 shows how a new FederationHost process is launched according tothe invention;

FIG. 8 shows how a federation is joined by a new client assuming thatthe repeater router is not overloaded;

FIG. 9 shows how a federation is joined by a new client assuming thatthe repeater router is overloaded and must start a new process on a newrouter;

FIG. 10 shows how packets are forwarded to other FederationHosts;

FIG. 11 shows how a routing system according to the invention scaleswith the total number of connections, which are typically distributed inhardware located across the larger Internet; and

FIG. 12 shows how a user controlled client application might providecontrols for selection of different channels from one or many differentsources.

DETAILED DESCRIPTION OF THE INVENTION

This invention broadly resides in a network computing environment andmethod that facilitates many-to-many data streaming with substantialmessage culling as well as more standard network optimization such asconventional multicast and Internet host packet routing throughinsertion of message traffic or application-specific applets into themessage routing system (or into routers). The approach allows a verylarge (i.e., greater than 100,000) number of client applications tocommunicate logically through a multicast cloud over a common carriersuch as the Internet to implement massive groupware configurationsincluding distributed simulations, games, and clientselectable/controllable data services used to broadcast audio, video, orother digital data.

Key innovations of the method include the following:

1) To insert a repeater router (or server cluster) into the Internetbackbone to eliminate client packet output replication in favor ofsending output packets to the repeater router, which in turn, replicatesthe packets to the relevant clients. This function with no packetculling is equivalent to multicast implemented by Internet routers thatsupport multicast, but in networks without multicast routers, thisfunction can be implemented by plug-in server which accepts packets andreplicates each pack from a particular input client (i.e. IP address) toa list of output clients (i.e. output IP addresses). The address listfor each input client is established through a connection protocol thatallows the client or a third-party brokering server to associate anoutput IP address list with each input IP address.

2) To insert rules (or message flow triggered applets) into the repeaterrouter which can decode input packet data and use this information tocontrol replication (i.e. applications-specific programming code whichimplements packet routing service quality, routing, and culling).Examples of such culling rules include the following: (a) Each clientcan continuously predict where an object simulated by another clientwill be absent of control input. If the error between prediction andactual is small enough, the repeater router need not forward any statechange packets from source client to destination client. (b) If thedestination client has a viewing port then no data from source clientswhich are outside of the destination client view port need be forwarded.(c) If the destination client is beyond a certain range from the sourceclient no data need be forwarded from out-of-range source clients needbe forwarded.

3) To provide a brokering server (or server cluster) which can provideto the repeater router address lists which connect each source client toits destination clients and provide the applets (in the specific case,the packet decoding and culling rules) to the repeater router whichallow the repeater router to only forward packets needed based ondestination client visibility requirements. Culling rules or code can beprovided by any qualified host, client, broker, or a designated networkcontrol host.

The communications system for implementing distributed simulationspecifically, and other applications where the routing element includesapplications data stream dependent information in its routing decisions,is based on extending the concepts defined by the High LevelArchitecture” (HLA) defined in Defense Modeling and Simulation Office,High Level Architecture Rules Version 1.0, US Dept. of Defense, August1996. HLA in its defined form is a general purpose architecture forsimulation reuse and interoperability. It consists of three parts: (1)HLA Rules, (2) HLA Interface Specification, and (3) Object ModelTemplate Specification. HLA in a client applications is implementthrough the applications programming interface embodied by the Run TimeInfrastructure or RTI.

HLA rules define HLA, its components, and the responsibilities offederates and federations. The official document can be found athttp://hla.dmso.mil/tech/rules.html. The HLA Interface Specification isa language independent specification for the HLA functional interfacesbetween federates and the runtime infrastructure (RTI). The officialdocument can be found at http://hla.dmso.mil/tech/ifspec.html. Asimulation client, or one of many simulations which are joined in theirexecution, is called a federate. A group of these clients together iscalled a federation. HLA defined interoperability of federates (i.e. howa federation works), and allows for multiple execution of simultaneousfederations.

To support its general goals, the HLA requires that federations andindividual federates be described by an object model which identifiesthe data exchanged at runtime in order to achieve federation objectives.This is called the Object Model Template Specification (OMT). The HLAOMT provides a template for documenting HLA-relevant information aboutclasses of simulation or federation objects and their attributes andinteractions. This common template facilitates understanding andcomparisons of different simulations and federations, and provides theformat for a contract between members of a federation on the types ofobjects and interactions that will be supported across its multipleinteroperating simulations. The official document on OMT can be found athttp://hla.dmso.mil/tech/omtspec.html.

The implementation of The RTI or Run-Time Infrastructure softwareprovides a set of services which are used by federates to coordinatetheir operations and data exchange during a runtime execution. The firstRTI enable client also serves as a federation broker to help newfederates join the federation (or leave it). The RTIs within thefederation share federate contact data so the federation will persist aslong as any single federate stays connect into it.

Like DMSO's HLA specification, this invention includes an RTI, or runtime interface, to the client simulation application. In small localarea simulations, our RTI can operate just as the DMSO version does(i.e. no centralized or specialized communications processes—just acommunity of federates endowed with a common RTI). However, whenfederations which span the Internet are contemplated, two additionalfunctions are present. FIG. 1 shows the structure of the RTI implementedper the DMSO specification. FIG. 2 shows an implementation whichcontains a separated routing function and a lobby manager function.

The lobby manager function or broker takes charge of joining and exitingfederations. The routing function which accepts all communications toand from a federate with its federation. The routers are aware of allconnected federates within a federation and can be replicated and placedat convenient points within the Internet backbone (typically within datacenters). Since each router services or concentrates communication toand from a maximum number of federates, the routers also know how topackage and route data to and from each other simulating the totalmulticast connectivity assumed in the original DMSO implementation ofHLA. In addition, since each router sees the data streams to and fromall of its assigned federates, it can operate quality of service ruleswhich control routing performance based on application-dependent rules.This substantially reduces backbone (between routers) and federateconnection (from router to federate or simulation client) bandwidth.

The preferred RTI (the “Cybernet RTI”) can be used under with anysimulation operating system including Microsoft Windows 9x, Windows NT,and Windows 2000. The RTI is implemented by two distinct code modules:the HLA-RTI.DLL (in Windows systems a file with suffix DLL is a codelibrary) and LobbyManager.exe (in Windows a file with suffix .exe is anexecutable program or process—in this case it implements the lobbymanager function).

LobbyManager.exe is a command line application. It maintains a list ofrunning federations. Applications can call LobbyManager.exe by remoteprocedure calls (RPC calls to get information such as a complete list ofrunning federations, the host machine for each federation, etc.Alternative implementation of remote messaging and request for procedureexecution, perhaps through direct socket connections from called processto LobbyManager process will be possible and acceptable. HLA-RTI.DLL islinked into the client application or federate at build or run time.

When hosting a federation (typically within a local network-typesetting), it can maintain a list of federates in the federation, or(typically in the Internet setting) can let a FederationHost processspawned by LobbyManager to maintain this list. The host (either HLARTI.DLL itself or the FederationHost process) reads and parses the FEDfile to initialize a list of message object classes as well as to definea list of interaction classes. Subsequently the HLA RTI.DLL orFederationHost process maintains these lists for the federation andkeeps track of published and subscribed object and interactions of eachfederate. When reliable data transmission is required, the HLA RTI.DLLor FederationHost process distributes data to each federate. One or theother (implementing the lobby manager function) also acts as a clientfederate for the local computer that is doing the hosting. When actingas a client federate, the lobby manager function connects to thefederation host, and provides all RTI interface API's to theapplication.

The FED file in this implementation is labeled with a suffix of “.FED”.This file is compatible with the DMSO FED file format so it can becreated and edited with “Object Model Development Tool (OMDT)” fromAegis Research or simply as an ASCII file with any text editor. Anexample of what goes in this file to define objects and interactionclasses is “HelloWorld.fed” from DMSO available fromhttp://hla.dmso.mil. The following values (stored in the registry in aWindows system) can be modified to customize the installation into afederate by functions provided in the HLA DLL Library (i.e. from in theSoftware Development Kit or SDK). The implementer of a clientapplication might provide the means for a game user to modify theseparameters (for instance by including a dialog box in the application toallow end user to modify parameters). These represent typical parametersan implementer might change:

-   1. Address. IP address for the machine on which the LobbyManager    runs. For example, 192.168.0.2-   2. Port. Port that LobbyManager uses. The default is “2000”. It is a    string value.-   3. Address. Multicast IP address. The default is 224.9.9.1.-   4. Port. Multicast port base value. The default is 22500. It is a    DWORD value. This base address is used by LobbyManager to    acknowledge its own existence. Each federation receives a multicast    port address from the LobbyManager, which is larger than the base    value and smaller than or equal to the maximum port number.-   5. MaxPort. Maximum multicast port number. The default is 23500.    When all ports between the base port and this port are used up, no    more federations can be created.-   6. TTL. Multicast TTL.-   7. NICAddress. Network interface card IP address. This can be useful    when multiple NICs are in a machine.-   8. QueueSizeLimit. Multicast is used for “best effort”    communication. Multicast packets are placed in a queue when they    arrive. If the queue size has reached this limit, new packets will    be abandoned.-   9. Address. This is a network interface card IP address that is used    when hosting a federation. It can be useful on a multiple NIC    machine.-   10. Port. This is used for TCP connections while hosting a    federation.

The LobbyManager process must be started either as a stand-aloneapplication (which would be typical for Internet play—FIG. 2) or byspawning it from a client application (the first federate on a localnetwork for localized play—FIG. 1). The process reads the LobbyManagerstart-up values (on a Windows implementation in the LobbyManager sectionin the registry). Other than setting up these values if they need to bechanged from their defaults, client code does not need to do anythingmore for LobbyManager for local play. Starting the LobbyManager replacesthe “rtiexec” or “fedex” commands used in the DMSO implementation.

In the client or federate code, a HLA_13 RTI::CLobbyManager class mustbe created, making sure that this class is present at startup time aswell as shutdown time. At startup time, its “Init” member function iscalled to initialize it, and at shutdown time, its “DeInit” memberfunction is called to clean up. The prototype of the Init function isBOOL Init(BOOL fsearch, DWORD dwTime, BOOL fUseLocalAddress), where“BOOL fsearch” specifies whether to search for LobbyManager.exe viamulticast ping.

If the LobbyManager.exe has already started (as is the case when joiningInternet play), it is spawned by the first federate, fsearch should beset to FALSE. “DWORD dwTime” specifies how long to wait for a search tocomplete if fsearch is TRUE. If “BOOL fljseLocalAddress” is TRUE, it isassumed that LobbyManager.exe is running locally. Otherwise theassumption is that it is running at IP address specified in theregistry. “DeInit” does not take any parameters. Functions availableafter “Init” is called and before “DeInit” is called, are the same asthose defined in the standard DMSO RTI (examples are provided by DMSO,such as the “Hello world” sample program).

The Cybernet RTI is an SDK is compiled and linked with C++ applications,for instance, within Windows environments. It includes a setup programthat installs the necessary components for a developer. The CybernetRTIexample implementation is to be used with Microsoft Visual C++ version6.0. The code generated with CybernetRTI will run under MicrosoftWindows 9x, Windows NT 4.0, and Windows 2000.

The C++ header files that are included into client applications areRTI.hh, RTITypes.hh, LobbyManager.h, and HLA_RTIProfile.h. They areplaced in the <Installation Directory>\include. The only differencebetween RTI.hh, RTITypes.hh and the comparable versions from DMSO isthat static functions use “fastcall” declaration specifications. Otherinclude files are that same as those available from the DMSOdistribution of HLA.

There is one lib(brary) file that is linked into the client application.This is HLA_RTI.lib. It is placed in <Installation Directory>\lib.Following we use the “HelloWorld” example from DMSO to illustrate howthe client application is built. In a client application that uses RTI,the first few things the client includes are declarations for aHLA_RTI::CLobbyManager class, a CFederateAmbassador class (see PROGRAMLISTING 1), and a text string char *szFederateName that uniquelyidentifies the federate.

The CFederateAmbassador FedAmb class is derived fromRTI::FederateAmbassador, and overloads some of theRTI::FederateAmbassador member functions. These overloaded functions arecallback functions. When something happens on the network, one of thecallback functions will be called. Some of the most useful ones arelisted below:

void CFederateAmbassador::startRegistrationForObjectClass (RTI::ObjectClassHandle theObjectClass) throw(RTI::ObjectClassNotPublished, RTI::FederateInternalError) ;

This function is called within a federate when another federate on thenetwork is interested receiving data from objects of this class whichthe first federate publishes. A federate registers for objects in thisclass to signal to another federate which publishes in the class that itwishes to see state updates as they publish.

void CFederateAmbassador: :stopRegistrationForObjectClass (RTI::ObjectClassHandle theObjectClass) throw(RTI::ObjectClassNotPublished, RTI::FederateInternalError) ;

This function is called when no client on the network is interested inreceiving data from objects in this class which a federate publishes. Afederate can unregister objects in this class published by another.

VoidCFederateAmbassador::turnInteractionsOn(RTI::InteractionClassHandletheInteraction) throw(RTI::InteractionClassNotPublished, RTI::FederateInternalError) ;

This function is called when a federate on the network is now interestedin the interaction another has published. A federate updatesinteractions in this class that is publishes.

VoidCFederateAmbassador::turnInteractionsOff(RTI::InteractionClassHandle theInteraction) throw(RTI::InteractionClassNotPublished, RTI::FederateInternalError) ;

This function is called when no client on the network is interested inthe interaction another publishes. A client stops updating interactionsin this class that it publishes.

void    CFederateAmbassador::discoverObjectInstance(RTI::ObjectHandle   theObject, // supplied C1 RTI::ObjectClassHandle    theObjectClass,// supplied C1    const char *theObjectName) // supplied C4throw(RTI::CouldNotDiscover, RTI: :ObjectClassNotKnown,   RTI::FederateInternalError) ;

This function is called when an object of a class to which a clientsubscribes is registered on the network. The client creates an objectlocally and stores “theObject.”

   void    CFederateAmbassador::reflectAttributeValues(RTI::ObjectHandle   theObject, // supplied C1    const RTI::AttributeHandleValuePairSet&theAttributes, //    supplied C4 const char *theTag) //    supplied C4throw(RTI::ObjectNotKnown, RTI::AttributeNotKnown,   RTI::FederateOwnsAttributes, RTI::InvalidFederationTime,   RTI::FederateInternalError) ;

This function is called when an object which a client had previouslydiscovered is updated. The updated values are in “theAttributes.” Theobject is identified by “theObject,” as specified in the previousfunction.

void CFederateAmbassador::reflectAttributeValues(RTI::ObjectHandletheObject, // supplied Cl  const class RTI::AttributeHandleValuePairSet&theAttributes,  const class RTI::FedTime &theTime, const char *theTag,struct  RTI::EventRetractionHandle_s) throw (RTI: ObjectNotKnown,RTI::AttributeNotKnown, RTI::FederateOwnsAttributes, RTI::FederateInternalError) ;

This function is the same as the previous one except it includes a timeinput.

void CFederateAmbassador::receiveInteraction(RTI::InteractionClassHandletheInteraction, const class  RTI::ParameterHandleValuePairSet&theParameters, const char *theTag) throw(RTI::InteractionClassNotKnown,RTI::InteractionParameterNotKnown,  RTI::InvalidFederationTime,RTI::FederateInternalError) ;

This function is called when an interaction which applies for a class towhich a client has subscribed is updated on the network. The updatedvalues are in “theParameters.”

void CFederateAmbassador::receiveInteraction(RTI::InteractionClassHandlethe Interaction,  const class RTI::ParameterHandleValuePairSet&theParameters,  const class RTI::FedTime &theTime, const char * theTag,struct  RTI: EventRetractionHandle_s theHandle) throw(RTI::InteractionClassNotKnown, RTI::InteractionParameterNotKnown, RTI::FederateInternalError) ;

This function is the same as the previous one except it includes a timeinput.

void CFederateAmbassador::removeObjectInstance(RTI::ObjectHandletheObject,const char *theTag) throw (RTI::ObjectNotKnown,RTI::InvalidFederationTime, RTI::FederateInternalError) ;

This function is called when an object that a client previouslydiscovered is removed. The object is identified by “theObject,” asspecified in “discoverObjectlnstance.”

void CFederateAmbassador::removeObjectInstance(RTI::ObjectHandle theObject,const class RTI::FedTime &,const char *theTag, struct RTI::EventRetractionHandle_s) throw(RTI::ObjbectNotKnown,RTI::FederateInternalError) ;

This function is the same as the previous one except it includes a timeinput.

void CFederateAmbassador::provideAttributeValueUpdate(RTI::ObjectHandle theObject, const class RTI::AttributeHandleSet &theAttributes)throw(RTI::ObjectNotKnown, RTI::AttributeNotKnown,RTI::AttributeNotOwned, RTI::FederateInternalError) ;

This function is called when a federate on the network requests thatanother subscriber update data for an object that has been alreadyregistered. The object is identified by “theObject,” as specified in“discoverObjectlnstance.”

void  CFederateAmbassador::turnUpdatesOnForObjectInstance(RTI::Object Ha  ndle theObject,const class RTI::AttributeHandleSet  &theAttributes)throw(RTI::ObjectNotKnown,RTI::AttributeNotOwned,RTI::FederateInternalError) ;

This function is called when a client on the network is now interestedin data from an object that the sourcing client previously registered.The object is identified by “theObject,” as specified in“discoverObjectlnstance.” The sourcing client application startsupdating of this object on the network.

void  CFederateAmbassador::turnUpdatesOffForObjectInstance(RTI::ObjectH andle theObject,const class RTI::AttributeHandleSet  &theAttributes)throw(RTI::ObjectNotKnown,RTI::AttributeNotOwned,RTI::FederateInternalError) ;

This function is called when no client on the network is interested inan object that sourcing client has previously registered. The object isidentified by “theObject,” as specified in “discoverObjectlnstance.” Thesourcing client stops updating of this object on the network.

PROGRAM LISTING 2 illustrates how a client publishes and subscribes to aobjects and their data usingf “PublishAndSubscribetoObjects.”

The CheckExitSignal function's prototype is “BOOLCheckExitSignal(void);”. It is a very simple function that may be usedin a command line application or it may be simply used as follows

-   BOOL CheckExitSignal (void) {return (_kbhit ( )==0);}

If it is a GUI application, it may be used as:

-   BOOL CheckExitSignal (void) {return fExit;}

where BOOL fExit=FALSE initially and is set to TRUE when WM_QUIT isreceived.

The following are descriptions of key Interface Classes. TheHLA_RTI:Cprofile class is declared in HLA_RTIProfile.h. All members inthis class are static. All registry section name strings and entry namestrings, along with default profile values are declared within it. Thefollowing are examples:

static UINT MS_FASTCALL GetInt(LPCTSTR lpszSection, LPCTSTR lpszEntry,int nDefault) ;  Example:  DWORD dwMaxPort =  HLA_RTI:CProfile::GetInt(HLA_RTI:CProfile::m_szMCastSection  ,HLA_RTI: CProfile::m_szMCastMaxPortEntry,   DEFAULT_MAX_MCASTPORT) ;static CString MS_FASTCALL GetString(LPCTSTR lpszSection,LPCTSTR lpszEntry,LPCTSTR lpszDefault) ;  Example:  CStringszLobbyManagerAddress  =HLA_RTI:CProfile::GetInt(HLA_RTI:CProfile::m_szLobbySectio  n,HLA_RTI:CProfile:: m_szLobbyAddrEntry, “192.168.0.1”) ; static BOOLMS_FASTCALL WriteInt(LPCTSTR lpszSection, LPCTSTR lpszEntry, int nValue);  Example:  HLA_RTI:CProfile::WriteInt(HLA_RTI :CProfile::m_szMCastSection,HLA   _RTI:CProfile::m_szMCastMaxPortEntry,dwMaxport) ; static BOOL MS_FASTCALL WriteString(LPCTSTR lpszSection,LPCTSTR  lpszEntry, LPCTSTR lpszValue) ;  Example: HLA_RTI:CProfile::WriteString(HLA_RTI:CProfile::m_szLobbySection,  HLA_RTI:CProfile:: m_szLobbyAddrEntry,   szLobbyManagerAddress) ;  TheHLA_RTI:CLobbyManager class is declared in LobbyManager.h. void DeInit(void) ;

This function is called when exiting RTI code.

-   BOOL Init (BOOL fSearch, DWORD dwTime, BOOL fUseLocalAddress);

This function is called when initiating RTI code. BOOL fsearch:specifies whether to search for LobbyManager.exe via multicast ping ornot. If the caller knows a LobbyManager.exe has already been started, orit is going to start it, the caller can set fsearch to FALSE. DWORDdwTime: is used if fsearch is TRUE to specify how long to wait for aresponse from the LobbyManager to the search request. BOOLfUseLocalAddress is TRUE, if the caller assumes that LobbyManager.exe isrunning locally (on the same machine making the call). Otherwise thecaller assumes that the LobbyManager is running at an IP addressspecified as a start-up value (in the registry for Windows).

-   static BOOL MS_FASTCALL IsLobbyManagerRunning (void);

This function checks to determine if LobbyManager.exe is running.

-   static void MS_FASTCALL ShutDown (void);

This function will shutdown LobbyManager.exe.

The extensions provided by this invention modify the functionality ofthe LobbyManager and support multiple routing functions which aggregatetraffic to and from clients and forward that traffic to other clients orrouters based on application dependent evaluation of the messagingstreams (based on culling rules). The changes and extensions toimplement this functionality are described in this section.

In DMSO version of the RTI, a list of active federation executions ismaintained by an executable called rtiexec. Every federation executionis created and destroyed by rtiexec. In Cybernet's version of RTI,described in the previous section, rtiexec is replaced by LobbyManager.Besides simply replacing rtiexec, LobbyManager also has the followingextended features:

Additional APIs

Additional Runtime Options

Mtunnel/FederationHost functionality

LobbyManager can be called directly from an RTI enabled clientapplication or federate by RPC (Remote Procedure Call or otherequivalent communication mechanism) to obtain information about the listof active federation executions. The following are member functions ofHLA_RTI::CLobbyManager class, which is declared in LobbyManager.h:

-   static BOOL FedexExist (const char *pExecutioName);

This function can be called to see if a federation named withpExecutionName already exists. It returns TRUE if it exists, and FALSEotherwise.

static int FindLobbyMember(const char *pLobbyMemberName, _SLobbyMember*pLobbyMember) ;

This function can be called to retrieve information about a federationnamed with pLobbyMemberName. It returns TRUE if successful, and FALSEotherwise. The requested information is returned in pLobbyMember. Thememory space of pLobbyMember is provided by the caller.

-   static CString * GetHostID (const char *pszHostName);

This function retrieves the application-specified ID of a host of afederation named with pszHostName. It returns NULL if failed.

static BOOL GetHostInfo(const char *pExecutionName, unsigned char szAddress [16], unsigned char szPort [8]) ;

This function retrieves information needed for making a TCP connectionto the host of a federation named with pExecutionName.

static CString *GetModelName(const char *pszHostName, const char *pszID);

This function retrieves the application-specified model name of anobject with ID specified by pszID in a federation hosted by pszHostName.It returns NULL if failed.

static BOOL GetFederateList(const char *pLobbyMemberName, CTypedPtrList<CPtrList, CString *> *pStringList) ;

This function retrieves the list of federates in a federation hosted bypLobbyMemberName.

-   static int GetLobbyMemberCount (void);

This function retrieves the number of hosts available.

-   static int GetLobbyMemberNames (long 1BufferSize, char *pBuffer);

This function retrieves the names of all available hosts. Each name is astring of 32 bytes in length with NULL-termination.

-   static CString * GetScenarioTitle(const char *pszHostName);

This function retrieves the application specified scenario title of afederation hosted by pszHostName.

BOOL JoinGameLobby(const char *pszModelName, const char *pszID, const char *pszScenarioTitle, CFederateList &FederateList) ;

This function is called implicitly if not called explicitly beforecreating a new federation. Calling it directly before creating a newfederation gives the application option to store additional informationabout a federation into the federation list maintained by LobbyManager.

-   void SetHostListChangeCallbackProc (HostListChangeCallbackProc    pProc);

This function allows application to setup a callback function. Whenthere is a change in the list of federations, the application will benotified via the callback function. Additional run-time features whichsupport Internet gaming allow the LobbyManager to be placed on a “brokerserver” computer to manage larger networks of federations over theInternet. The first feature for such purpose is user authentication. Anapplication can use the “Login” member function ofHLA_RTI::CLobbyManager class to login to LobbyManager, and the “Logoff”member function to log off. HLA_RTI::CLobbyManager is declared inLobbyManager.h. Alternatively the user “login” can be accomplished via agame-specific web site which is authenticated as a site when the site(through CGI) logs into the LobbyManager through a secure command lineinterface.

LobbyManager can keep track of a list of “repeater router” machines.Each “repeater router” machine is running a copy of MTunnel to bediscussed later. One task of MTunnel is to launch new processes ondesignated repeater router machines which are placed in data centersdistributed about the Internet (based on backbone and client-to-routingmachine load balancing considerations) for LobbyManager.

If a user requests to create a new federation, or to join an existingfederation that already has too many members, a new federation hostprocess will be launched on a repeater routing machine. AllFederationHost processes for the same federation on various routermachines are able to communicate and route client messages from one toanother and each has information about each entire federation withinwhich it operates. FIG. 3 provides a process flow of these operations.

For example, if a client requests LobbyManager to create a federationcalled “Fed1”, LobbyManager makes sure that there is no federationcalled “Fed1” on its network and then it creates a hosting process forthe federation “Fed1” on repeater router 1 which might be called“FederationHost1”. When another client requests to join “Fed”, it willbe assigned to FederationHost1 on repeater router1. As more and moreclients join “Fed1,” the LobbyManager at some point will decide tocreate another process called “FederationHost2” on repeater router 2 tohost the same federation, namely “Fed1,” and will direct newer clientsto FederationHost2 as the host. “FederationHost1” and “FederationHost2”share the same client list, the same object list, etc. Each will performculling functions for the connected clients for which it is responsible.

Suppose that a client requests to create another federation called“Fed2.” The LobbyManager makes sure that there is no federation called“Fed2” already defined on its network. Then it find the least busyMtunnel router, say repeater router and creates a new FederationHostprocess called FederationHost2 on repeater router1. When another clientrequests to join “Fed2,” it will be assigned to FederationHost2 onrepeater router1. Router support for “Fed2” will be grown based on thenumber of new connections just as it was for “Fed1.” FIG. 4 shows asample network connecting seven (7) clients to one of two repeaterrouters, through a single LobbyManager. Because FederationHost1 isimplemented across the two repeater routers, they must be incommunications to route messages from Fed1 clients on one to the otheras needed.

When managing a large network of federations over the Internet,LobbyManager will spawn as many FederationHost processes as needed tohost a federation.

FederationHost is an executable, but it cannot be run by itself. It isalways launched on a free router by LobbyManager through a process namedMTunnel.

FederationHost performs all the host functions defined in the RTI codepreviously described. When there are multiple FederationHosts for agiven federation, they communicate with each other via both TCP/IPconnections and IP multicast. They will each maintain a complete list offederates, but each will communicate directly with a limited number ofthese clients.

Exactly which clients will communicate with a given FederationHost isdetermined by LobbyManager. The client code in HLA_RTI.DLL receives theIP address of an Mtunnel router and a port address of a FederationHostProcess from the LobbyManager after it logs in. Then the client codewill establish a TCP connection with the FederationHost (for reliablemessages) as well as a UDP connection (for lower priority state changemessages).

Because clients do not communicate directly with each other, networktraffic is greatly reduced. For example, if FederationHost 1 on repeaterrouter 1 is hosting 10 users, and FederationHost 1 on repeater router 2is hosting 10 users, for the update of the status of a single clientconnected to repeater router 1, there is going to be one and only onetransmission of data from repeater router 1 to repeater router 2. Thestatus update does not need to be done 10 times for each clientconnected to repeater router 2 between the repeater routers. This isdiagramed in FIG. 5.

FederationHost also performs the function of message culling to furtherreduce network traffic. Culling functions, which are typicallyapplication dependent, are defined as “member functions” of variousattribute sets in FED files, which reside on repeater routers. Theseattribute set definitions are provided by the repeater router builder orapplications developer in a FOM (Federation. Object Model) library. Eachfunction can be turned on and off at run-time. Certain culling functionscan have parameters to be set at run time as well. Because one canderive new attribute sets from existing ones, modeling C++ classderivation with single inheritance, we can create other attribute sets,and are not limited to what has been included in the base FOM library.Some culling functions slow down message service if two clients are farfrom each other in virtual space (i.e. do not need frequent positionupdates because position changes over short periods are small relativeto mutual distance). Some culling functions exploit the fact thatclients project new object positions as a function of last position,velocity, and acceleration. Thus, if an object is both subject to asignificant control action, the difference between communicated statemessages and the estimated position might be slight enough that themessages need not be forwarded. Other mutual visibility considerationsgenerate culling rules, depending on the application. For instance,sometimes it is useful t divide the game space into zones. Within alocalized zone, locations can be coded relative to the zone origin, andvisibility might be restricted to only other objects in the same zone.Any and all of these culling functions can be implemented into themember functions in the FOM.

Referring to FIG. 6, if we start with “CybernetBaseEntity”, whichconsists of double Altitude, double Latitude, and double Longitude, wecan define a culling “member function called “CheckCube” for“CybernetBaseEntity”, which is defined as “Altitude-Altitude0>=a1 andAltitude-Altitude0<=a2 and Latitude-Latitude0>=b1 andLatitude-Latitude0<=b2 and Longitude-Longitude0>=c1 andLongitude-Longitude0<=c2”, where (Altitude0, Latitude0, Longitude0) is a“CybernetBaseEntity” that belongs to the receiving federate. Also a newmember function, namely EableCulling, is added to RTI::RTIAmbassadorclass. It allows applications to turn certain culling rules on and off.

The MTunnel is an executable process running on a repeater router. Eachrouter has one and only one MTunnel process running. When LobbyManagerneeds to launch a new FederationHost process on a repeater router, itconnects to MTunnel process on that repeater router using TCP/IP, andsends the request. MTunnel will launch the requested new FederationHostprocess and return the status of the new process to LobbyManager, sothat a client application such as a game simulator can connect with theFederationHost process. FIG. 7 shows how a new FederationHost process islaunched. FIG. 8 shows how a federation is joined by a new clientassuming that the FederationHost router is not overloaded. FIG. 9 showsshows how a federation is joined by a new client assuming that theFederationHost machine (repeater router) is overloaded and must start anew FederationHost process on a new router. The game shown in thefigures is OpenSkies, but this game can be replaced with any other.

Besides acting as a process launcher, Mtunnel also forwards IP multicasttraffic from one repeater router to another using unicast, simulatingmulticast routing between Mtunnels, when an IP multicast connection isnot available between routers. It selects routes of least travel for allforwarded data. FIG. 10 shows how packets are forwarded to otherFederationHosts.

Combining FederationHost with Mtunnel processes, we can reduce networktraffic through the Internet backbone considerably. If the topologyamongst routers is such that a datagram can reach every node with asingle pass on every connection segment, the amount of data sent acrossthe Internet is simply proportional to the number of clients. Considerthe example of a flight simulator. An aircraft needs to transmit itsaltitude, latitude, longitude in doubles, heading, pitch, bank infloats, and ID in 32 bit integer for a total of 76 bytes at 30 Hz, i.e.,220 bytes/sec, in UDP datagrams. This number can be further reduced bynot sending the high 32 word of each double every frame, for example. Sothe number becomes 64 bytes at 30 Hz, i.e., 192 bytes/sec. If there are100 players, the amount of data sent across the Internet backbone is100*192 bytes/sec=19.2 kilobytes/sec. For 500 users, it is about 96KB/sec.

Local traffic at each router will still be n-squared times 192 bytes/secwith the absence of culling. However, due to the limited bandwidth thatis available to each end user, we further rely on culling tosignificantly reduce the amount of data sent to each user. Assume thatthe user is using a 56 kb/sec modem, the number of aircraft it canhandle is about 10-15. Since we must leave room for infrequentlytransmitted data, plus things such as missiles and other projectiles,culling will limit the number of planes to 10. Cybernet FOM library isimplemented to support substantial network traffic culling. Therefore,unlike general-purpose attribute set definitions, each variable type isspecified. For detailed specifications of general-purpose attribute setdefinitions in Government defined DMSO FED files, refer tohttp://hla.dmso.mil/sdc/rti/rting-13v2/refD.pdf. The only deviation inthe preferred embodiment described here from the DMSO FED specificationis the addition of culling rules and specification of variable types.

The following is a example list of the content of Cybernet FOM libraryin alphabetical order. Other culling rules in addition to CheckSquareand CheckCube can be defined on an application specific basis withinthis framework.

1. CBaseEntity2D (class CBaseEntity2D  (attribute x besteffort receive) (attribute y besteffort receive)  (culling CheckSquare double x doubley) ) 2. CBaseEntity. Derived from CBaseEntity2D. (class CBaseEntity (attribute z besteffort receive)  (culling CheckCube double x double ydouble z) )

A key innovation in the system implemented as the preferred embodimentis that the distributed network of client applications communicate toeach other through reapter routing systems. These systems provide ameans for connecting/disconnecting from the federation of simulationnetwork (the LobbyManager) and for routing messages from client toclient through the mediation of the routers (Mtunnel and FederationHostprocesses). The LobbyManager scales by simulation network (i.e.application or game and the number of “parallel” game universes orfederations defined by the game operator or the players, depending onhow the application space is implemented by its developer). The routingsystem scales with the total number of connections, and as shown in FIG.11, is typically distributed in hardware located across the largerInternet (or alternatively can be co-located in a single location ofnetwork). Spreading of the routing resources optimized transmissionbandwidth lower by:

-   (1) providing points of concentration so that all clients need not    connect directly to each other-   (2) providing intelligent gateways which can apply culling rules so    that messages which would not be relevant to a particular client can    be sent a a reduced quality of service or not at all

The technology in the preferred embodiment—is designed to implementmassive distributed games and simulations, however, the technology isequally valuable in implementing other massive groupware Internetapplications with similar characteristics. These characteristics are:

-   (1) many source clients producing messages or data streams for many    destination clients-   (2) many messages produced will not be useful at destination client    depending on setting or controls which are available to the    destination user, but not directly to the source-   (3) routing points through which each source client sends and each    destination receives and between which a concentrator or routing    protocol can be used (to move bulked messages between routers when    the source and the destination connect through different ones)-   (4) algorithms or culling rules which can eliminate or reduce    quality of service to specific message streams to specific    destination clients based on the contents of streams from the source    and destination clients (since both destination and source clients    communicate through the router which implements the rules, both can    be consider sources for the purpose of rule execution).

Another example of an application which fits this model is distributionof user customizable video, audio, or other digitized information (likemedical data). The user controlled client application might providecontrols for selection of different channels from one or many differentsources (FIG. 12). Only a single feed need be forwarded through therepeater router based on the router's understanding of the controlssettings made by the user's player application. For instance, assume ten(10) video capture servers code video streams from ten alternate viewinglocations at a sporting event. The user selects at his/her viewingstation which stream(s) are relevant to him/her. All streams are sent toa router for distribution (because different users may select views fromany of the streams), but because the router knows which views arerelevant to which viewers, only some data is forwarded through therouter to each user client. This technology might be implemented viaconventional multicast routing optimized for fast multicast group jointand unjoin functions, but the preferred embodiment in this disclosure isa preferred application when there are hundreds and perhaps thousands ofsources and millions of destinations. In that setting the disclosedapproach reduces total aggregate bandwidth orders of magnitude.

I claim:
 1. An Internet-based system for implementing massive groupwareapplications, comprising: a plurality of computer-based clients, eachclient including a processor and memory with instructions stored in thememory and executed by the processor to implement a groupwareapplication; one or more repeater routers, each repeater router beingoperative to receive input data packets from at least one of the clientsand perform the following functions: decode the input data packets andreplicate the packets in accordance with a set of rules, and forward thereplicated packets as output data packets to other clients based upon aconnection protocol; and one or more lobby managers providing andupdating the rules and connection protocol to each repeater router sothat each repeater router only forwards packets to relevant clientsassociated with the groupware application; and wherein the set of rulesincludes a rule that each client may continuously predict where anobject simulated by another client will be absent of control input, andif the error associated with the prediction is sufficiently small, therepeater router need not forward any state change packets from sourceclient to destination client.
 2. The system of claim 1, wherein therepeater routers further support conventional packet-routing betweenclients on a peer-to-peer basis.
 3. The system of claim 1, wherein theconnection protocol implements a routing address list.
 4. The system ofclaim 1, wherein the rules are applet-based.
 5. The system of claim 1,wherein the groupware application is a distributed simulation or game.6. The system of claim 1, wherein the groupware application is a clientselectable and controllable data service associated with thedistribution of audio, video, or other digital signal stream.
 7. Thesystem of claim 1, wherein the clients enter and leave through a lobbymanager.
 8. The system of claim 1, wherein the lobby manager is furtheroperative to validate the groupware application in terms ofcompatibility and download data to correct for deficiencies.
 9. Thesystem of claim 1, wherein the repeater routers further implementapplication-specific message culling to reduce client-cloudcommunications.
 10. The system of claim 9, wherein the message cullingincludes message omission, rerouting, and other quality-of-serviceconsiderations.
 11. The system of claim 1, wherein the repeater routersfurther support one or more conventional multicast protocols.
 12. Thesystem of claim 1, wherein each lobby manager is operative tosimultaneously process one or more federations for gaming or otherapplications.
 13. The system of claim 12, wherein the federationscommunicate through multicast or replicated unicast protocols.